1. Field of the Invention
The present invention relates to a mass spectrometric analysis system and method using a mass spectroscope.
2. Description of the Related Art
In general mass spectrometric analysis, after a sample of measurement target is ionized, various types of ions generated are transferred into a mass spectroscope. Then, the ion intensity is measured for each mass-to-charge ratio (m/z), i.e., ratio of mass number m to valence number z of each ion. The mass spectrum acquired as a result of this measurement includes peaks (i.e., ion peaks) of the ion intensity measured with respect to each mass-to-charge ratio. Performing the mass spectrometric analysis of the ionized sample in this way is referred to as “MS1”.
In the tandem mass spectroscope capable of performing multi-stage dissociation, the ion peak having the value of a certain specific mass-to-charge ratio m/z is selected (the selected ion type is referred to as “parent ion”) from among the ion peaks detected by MS1. Moreover, the parent ion is dissociated and decomposed by an operation such as collision with gas molecules. Then, the mass spectrometric analysis is performed for dissociated ion types generated, thereby acquiring the mass spectrum similarly. Here, dissociating the parent ion over n stages then to perform the mass spectrometric analysis of dissociated ion types generated is referred to as “MSn+1”. In this way, in the tandem mass spectroscope, the parent ion is dissociated over the multi stages (i.e., first stage, second stage, . . . , n-th stage), then performing the analysis of mass numbers of the dissociated ion types generated at each stage (i.e., MS2, MS3, . . . , MSn+1).
In the mass spectroscope capable of performing the tandem mass spectrometric analysis, in most cases, the parent ion at the time of performing MS2 analysis is selected from among the ion peaks acquired in MS1. At this time, the mass spectroscope is equipped with the following data dependent function: Namely, the ion peak is selected as the parent ion in the order of the ion peaks of the descending ion intensities, e.g., the ion peak whose ion intensity falls within the top-ten intensities is selected. Then, the dissociation and mass spectrometric analysis (i.e., MS2) is performed for the parent ion.
In the ion-trap mass spectroscope manufactured by Finnigan Corporation, the parent ion at the time of performing MS2 analysis is selected from among the ion peaks acquired in MS1. At this time, the ion-trap mass spectroscope is equipped with the following dynamic exclusion function: Namely, the ion type having a mass-to-charge ratio m/z value specified in advance by user is selected and avoided as the parent ion.
US 2001/0007349A1 (JP-A-2001-249114) and JP-A-10-142196 can be cited as publicly-known examples concerning judgments on coincidence degree between an ion type measured and a pre-measured ion type.
In US 2001/0007349A1 (JP-A-2001-249114), a characteristic ion peak within first-stage spectrum data and second-stage spectrum data on the ion type corresponding thereto are stored into a database. In the measurement thereinafter, the second-stage spectrum data stored in the database is compared with spectrum data acquired by second-stage mass spectrometric analysis of the measurement-target sample, thereby checking the coincidence degree. Then, data component having the highest coincidence degree is outputted as the comparison result.
In JP-A-10-142196, in the multi-stage dissociation measurement, the continuous measurement is performed with no intervention of a sample injection process during the measurement, thereby avoiding an ion-intensity variation caused by the data injection between MSn and MSn+1. This avoidance makes the addition of a standard sample unnecessary, thereby allowing implementation of the efficient quantitative analysis. In MSn and MSn+1 data analysis, MSn+1 measurement is carried out, or the measurement returns to MS1 measurement by checking whether or not the data coincide with specified ion data already collected.